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By Alistair James, Mo Shahsavari, Leon Botham

Recent catastrophic failures of heap leach facilities have revealed fundamental weaknesses in prevailing design paradigms, modeling toolkits, and oversight practices that continue to treat heaps as static, free-draining earthworks despite compelling evidence to the contrary. The core proposition advanced in this paper is that heap materials are intrinsically dynamic: their structure, permeability, and shear strength evolve under the sustained influence of irrigation, climate, and geochemical reactions, and these timedependent changes can precipitate abrupt transitions from granular stability to flow-like failure. Drawing on investigations of recent failures at Çöpler Mine in Turkey and Eagle Gold Mine in the Yukon, alongside earlier incidents in Peru, Arizona, Nevada, and Chile, the analysis identifies a recurrent sequence driving catastrophic behavior: progressive weathering elevates fines and suppresses permeability; drainage systems designed for initial conditions become overwhelmed; pore pressures rise heterogeneously within the heap; and static liquefaction initiates rapid mass movement with long runout. Current guidance, including ICOLD and ANCOLD frameworks and ASTM testing standards, provides a necessary foundation but is tailored to tailings and conventional soil mechanics. These documents offer insufficient direction for characterizing timedependent material degradation, quantifying rheology of weathered ore, and modeling post-failure mobility. To address this deficit, the paper proposes an integrated framework combining enhanced characterization, multi-physics numerical modeling that couples hydro-geochemical processes with large-deformation mechanics, and comprehensive monitoring with Trigger Action Response Plans. The conclusion argues for a heap-specific standard that embeds these elements from concept to closure, aiming to materially improve safety performance and reduce the likelihood and consequences of future failures.

Feb 22, 2026

By D. Brandt

The Dos Pobres Mine is a copper oxide heap-leach mine located near Safford, Arizona. Mine production is 180,000 tons (163,293 tonnes) per day with a stripping ratio of 2:1. During the startup phase of the mine, the required fragmentation size was easy to achieve as the ore was highly weathered and fractured near the surface. As the mine depth increased, the proper fragmentation size became harder to achieve due to less weathering and different rock types. Because copper recovery increases as crusher product size decreases, achieving the appropriate product size at the crusher is the operating priority. The Engineering Department started a project to improve fragmentation through blasting and thus increase throughput in the crushing system. It soon became clear that input from other departments was going to be required to make this a safe and economical project. Therefore the Crush and Convey and Ore Control departments worked together to evaluate all available data on blast patterns and explosive loads and tracked performance and results. Using image analysis, Drill Energy Index and databases, we have been able to improve fragmentation size and verify the results while controlling costs.

Jan 1, 2011

Mine planners must select a single pit for design with the knowledge that the grades on which this selection is made are uncertain. This uncertainty is often ignored through the use of deterministic models of grade. This makes the mine planner?s job simpler but does not necessarily lead to the ?correct? or ?best? selection. Grade uncertainty is typically modelled with conditional simulation which generates multiple possible realisations of grade that are equally probable (or improbable) to occur. Methods for incorporating grade uncertainty into mine planning to date have either been perceived as being too complicated, not accessible or too time consuming. This paper proposes a simple and efficient modelling approach to incorporating conditional simulation into pit optimisation, which would be able to be applied in currently commercially software. An example for Resolute Mining Ltd?s Syama Gold Project in Mali shows the range of ore, grade and value outcomes associated with generating pits through a variety of methods.

Feb 27, 2013

One of the most important parameters in mine ventilation planning is the friction factor (K). Accurate values of friction factors are critical especially when carrying out mine ventilation simulations. No computer simulation of a mine ventilation network is meaningful if the airway resistances are not accurately estimated (when planning a new mine) or measured (for an existing mine). However, in the first case not many reliable values of friction factors exist in the international literature. This paper presents the results of a research project carried out in the province of Quebec where ventilation friction factors were measured in all underground metal mines. These friction factors are statistically analyzed and tabulated. A friction factor database was created that also includes the friction factors measured in the past by other people. This database can help the mine engineer to accurately estimate ventilation friction factors according to the specific conditions. This database offers several values of friction factors typical for hard rock mine conditions typical of modern underground metal mines.

Jan 1, 2009

By Bruce Gellar

For the past six years, the author has made it a priority to attend the Prospectors and Developers Association of Canada’s (PDAC) annual conference. This most recent meeting took place March 10-13, 2002in Toronto, Ontario. In the three years since the author’s last PDAC report, the mining industry has undergone a severe trough. Some the industry’s woes included deeply discounted commodity prices, rampant layoffs, mergers, and overall avoidance by the investment community. However, at each of the PDAC conferences, the author has felt a heightened sense of excitement about the mining industry, more so than at other similar gatherings.

Jan 1, 2002

By A. B. Cecala

Enclosed cabs have been used on surface mining equipment for many years to protect equipment operators from health and safety hazards. The surface mining and quarrying process is a highly mechanized process that generates large quantities of respirable dust. Due to economic factors, more older mining equipment is being used today than in years past. With this older equipment, it is common to observe deterioration of many components on the enclosed cabs which greatly reduce their protection effectiveness. NIOSH has performed a number of different field studies, as well as a comprehensive laboratory study evaluating various factors and parameters regarding enclosed cabs. NIOSH has recently completed a cooperative research effort with Sy-Klone International and Vulcan Materials Company to evaluate the effectiveness of a newly designed uni-directional filtration and pressurization system that brings all the clean filtered air in at the roof of the cab and extracts all recirculated air near the floor. This design provides the highest air quality to the equipment operator. Testing on this new system showed an almost 10-fold reduction in respirable dust inside the enclosed cab. The uni-directional design is easy to incorporate and should be considered for all new and retrofit systems in surface mining equipment.

Jan 1, 2009

Several common ratios used for determining spontaneous combustion activity rely on comparing the amount of various products of oxidation with the amount of oxygen consumed to produce these products. As coal gets hotter, oxidation reactions become more efficient meaning more products produced for less oxygen consumed. There are many problems associated with accurately determining the true amount of oxygen used. These problems relate to the monitoring technique (and its associated uncertainties) used to generate the results, deficiencies in the established equations utilized in calculations, dilution with other gases and other sources of oxygen depletion. Typically the oxygen deficiency is over estimated, resulting in the under estimation of the indicating ratio. For this reason the use of ?one off? calculations to determine the status of the underground environment is not recommended. Instead trends of these ratios should be used to identify increases which indicate an increase in oxidation intensity. This paper outlines problems associated with the monitoring techniques and equations used to determine the oxygen deficiency.

Jan 1, 2009

By R. J. F. Goodfellow

Many underground projects now include preparation of a Risk Register through planning and design as a tool for project and risk management. There is still significant discussion within the industry as to whether and how to best present the Risk Register through the bidding process and the construction phase of a project. While the ITIG Code of Practice for Risk Management of Tunnel Works recommends this approach of continuity in risk management procedures, it is silent on the specifics of how this should be achieved. This paper will explore the perceived benefits and disbenefit of including the project Risk Register with bid documents; format and content that should be transferred and lessons learned using the case history of bidding and early construction phase of the Bi-County Water Tunnel in Montgomery County, MD

By J. F. Lupo

Heap and valley leach operations rely on solution collection piping placed within the heap to enhance both solution recovery and to assist overall solution management. The most common piping used in leaching operations is solid or perforated High Density Polyethylene (HDPE) pipe and Corrugated Polyethylene pipe (CPE). These pipes are widely used because of their low cost, ease of installation, durability, and flexibility. The typical recommended maximum design depth of burial for HDPE and CPE pipes is on the order of 30 meters (100 feet). However, ore heap heights at many facilities exceed 30 meters and some are now approaching 180 meters (600 feet) in height. At very high ore heap heights, the stability and performance of HDPE and CPE pipes becomes a critical issue for leaching facility design and operation. Failure of solution collection piping can lead to poor solution recovery, high hydraulic heads on the liner system, and in some cases, unstable ore slopes due to high solution pressures near slopes. This paper presents a review of methods that have traditionally been used to evaluate pipe stability under high normal loads. A common shortcoming of these methods is the inability to account for beneficial effects of ore arching around pipes and the time-dependent creep (stress relief) behavior of polyethylene (PE) materials. A new analytical approach is developed and presented which includes the effects of ore arching around pipes and creep of PE materials. The results of the new approach show that PE pipes will deform under high heap loads, but can remain stable and functional. Pipe stability is shown to be dependent on the type of pipe backfill and initial backfill compaction. The new approach represents a useful tool for designing applications for PE pipe under high normal loads.

Jan 1, 2001

By N. Aouad

Dump truck operators are exposed to whole-body vibration (WBV) levels that exceed the International Standard Organization (ISO) 2631-1. The WBV level measured by RMS acceleration value, for operator comfort, and long-term health and safety is under 0.315 m/s2 by these standards. However, fundamental research by Frimpong and Aouad (2009, 2012) and field experimental study by Kumar (1999) have shown that operators are exposed to extreme WBV levels exposing them to injuries and musculoskeletal diseases in the long-term. These extreme WBV values in the vertical direction are equal to 3.56 m/s2, 1.12 m/s2 and 0.87 m/s2 for the operator?s seat, lower-back and cervical regions, respectively. This paper will outline current research to solve these problems. Keywords: WBV, Truck Vibrations, MSC.ADAMS, Virtual Prototyping

Feb 27, 2013

By F. Díaz-Fierros, D. Rubinos, M. T. Barral

The present work explores the reutilization of red mud, an industrial waste arising from the production of alumina, as a component of isolation technologies for hazardous substances. The work involved the study and optimisation of the geotechnical properties of red mud in conjunction with adsorption experiments of As(V) and Hg(II). The results from both types of experiments were integrated in a dispersion-diffusion model to calculate migration curves and minimum thickness of the red mud compacted layer. The geotechnical studies showed that compaction increased the stability and decreased the hydraulic conductivity of red mud barrier. Red mud sorbed high amounts of As (up to 44 mmmol kg-1) and Hg (up to 9.2 mmmol kg-1). The calculated minimum thickness of the red mud barrier was 1-10 cm for As and 2-19 cm for Hg, for an operation period of 35 years. The results obtained let to conclude that the reuse of red mud as a component of isolation systems of hazardous substances represents a viable alternative use of this residue.

Jan 1, 2011

By T. Payne

Underground heat issues are mainly focused on the detrimental effects to a workers health. However, working in hot, humid conditions has other negative effects. Studies have shown that safety, productivity, workforce morale and operating cost are also worsened in these conditions. The human body has several mechanisms for rejecting heat and remaining cool. However, once the air temperature exceeds about 34°C, the only effective mechanism is by evaporation of sweat from the skin. This is assisted by acclimatisation which is the human body?s enhanced ability to combat extended exposure to heat. The body has to remain well hydrated when working in heat as even small degrees of dehydration cause significant decreases in the ability to work in heat. There are two ways in which heat load can be reduced: Through use of refrigeration/vent/cooling to reduce thermal stress on workers; Reduce the contribution that heat sources have to underground heat load (e.g. reduce idle time, fleet size, etc). Some of the sources of underground heat have the potential to be more manageable than others. Geothermal heat and heat from autocompression will be found in all mining situations in varying degrees depending on geothermal gradient and surface temperature, however, the use of equipment and blasting may be streamlined to reduce the underground heat load. It is through a combination of the available options that most mines will successfully control their heat related problems. Mt Isa, which has been a focus for heat related study in Australia, has successfully implemented protocols for working in heat. Through combining these with the installation of a surface bulk air cooling plant, Mt Isa has consistently reduced the incidence of heat illness. This is likely to be the most cost effective method of reducing heat load for deep mines in Australia. Shallower mines which may only occasionally encounter hot conditions should consider more portable cooling options. This study will review the heat issues in underground Australian metalliferous mines.

Jan 1, 2009

By H. Akbari

The ordinary Portland cement (OPC) is the key pozzalonic component of the concrete mix, widely used as the construction material world-wide. Billions of tons of OPC are used in the construction industry each year. However, calcinations of limestone and silica that produce OPC also produce almost an equal amount of CO2 during the cement manufacturing process. Thus, OPC production accounts for nearly 7% of all anthropogenic CO2 emission each year. The main objective of this study was to develop a geopolymer-based composite to be used as a substitute for OPC in concrete application to significantly lower the carbon foot print of the construction industry. A waste material produced during the coal combustion process was used as the main raw material for the geopolymer-based composite. It was mostly the non-metallic content of the F-type fly ash produced from the combustion of bituminous coal. The authors envisioned to extract some of the valuable metal oxides from fly ash prior to using the major non-metallic portion of the fly ash for geopolymer concrete application. The results obtained from this study exhibited that the compressive strength of the geopolymer concrete compares favorably with that of the conventional concrete prepared using the OPC.

Feb 27, 2013

By Don F. Macfarlane

This paper describes the field application of the NTH fracture classification to rock encountered in the construction of the 9.6 km long, 10m diameter, Second Manapouri Tailrace Tunnel. Excavation of the tunnel was undertaken by TBM between 1997 and 2002, in gneisses, granitic and diorite rocks. The paper outlines an adaptation of the NTH fracture classification used during the geological logging of this tunnel. The NTH fracture classification was primarily applied to assess discontinuity spacing for tunnel support requirement decision-making. The paper includes some general comparison of NTH classes with overall penetration rate.

Jan 1, 2008

By T. R. Paquin

Powerful, easy to manipulate, ventilation modeling software is readily available to most mining engineers. Too often when preparing an initial ventilation model, engineers will go overboard in their design, creating a complex model with hundreds of branches. When, in practice, the creation of a less complicated ?to the point? model, containing a few well-constructed branches, would have delivered the same results. In this paper the author will demonstrate, by using actual feasibility report examples, that when designing a ventilation model, engineers should make more use of the K.I.S.S. (?Keep It Simple, Stupid?) Principle. As mining industry consultants we must continue to improve on, and deliver timely and cost-effective results to our customers.

Jan 1, 2009

By K. Pathak

Loaders and dump trucks are the most commonly used surface-mining equipment. Negligence of the safety-engineering aspects of dump trucks may result in serious accidents in a mine. A reduction in the risk of an accident due to the deployment of trucks can he achieved by engineering analysis, risks assessment, improved safety features, active safety devices, condition-based maintenance, in-built protection systems, etc. This paper presents some cases of accidents in Indian surface coal mines and advocates a systems approach to safety.

Jan 1, 1999

By D. J. Kunz

Myanmar Ivanhoe Copper Company Ltd. (MICCL) has been operating the Sabetaung- Kyisintaung (S&K) Project producing LME Grade A Copper Cathode using the Heap Leach-SX-EW Process since 1998. The mineralization is mainly Chalcocite and the mine has a life of 20 years at the designed annual production of 25,000 tonnes of cathode copper. Design capacity was achieved within two of months of start-up. The mine is among the world’s lowest cost, Heap Leach-SX-EW operations. Information regarding plant design and operation are presented along with the challenges lying ahead and the latest developments. Daniel Kunz is President and Chief Operating Officer of Ivanhoe Mines, and a director of MICCL. He has more than 20 years’ experience in mining, construction and engineering. Prior to joining Ivanhoe Mines in 1996, Mr. Kunz was Vice President and Controller of Morrison Knudsen Corporation, a major international mining and construction company. He was also President and Chief Executive Officer of MK Gold Company, a public mining company listed on NASDAQ.

Jan 1, 2001

By P. Christmann

"In June or July 2005, the European Commission will present its Thematic Strategy on the Sustainable Use of Natural Resources proposal to the Council and European Parliament, one of the seven Thematic Strategies to be developed and implemented under the 6th European Environment Action Programme in support of the European Union’s Sustainable Development Strategy defined by the European Union’s Head of State at the Göteborg European Council, in June 2001. The time scale for this Thematic Strategy is 25 years (2005-2030). This paper discusses some of the key issues related to the EU minerals and metals industry that needs to be addressed by the Strategy. These are: - the need for access to mineral reserves in the EU and abroad; - the need to strenghten the capacity of developing countries to sustainably promote and regulate the use of their mineral potential; - the need for an EU mineral resources intelligence capacity. There are additional important needs, which are not discussed in this paper, such as: - the need to foster further innovation in mining, ore beneficiation and metallurgical technologies; - the need to integrate and simplify the exisitng complex regulatory framework applicable to the EU mining industry and to effectively implement existing legislation."

Jan 1, 2005

By R. W. Kobler

The pelletizing process for low grade iron ores has undergone continual changes since its inception over twenty years ago. These changes have necessitated filtration equipment changes in order to produce a product suitable for balling. With modern techniques it is now possible to produce pellets of 68% Fe from ores containing as low as 26% Fe. Low grade ores require fine grinding to liberate impurities This shift to finer grinds over the years has necessitated major changes in the filtration steps. Techniques are now available for producing suitable product from ores with Blaines as high as 3600 cm2/gram. This has been made possible by the development of high performance filters. Recent developments have reduced maintenance costs and produced higher production reliability. The paper discusses iron concentrate filtration from its beginning to present day design. It will be shown that the dewatering step prior to balling has gone through four generations of filters. Particular emphasis is placed upon hydraulic studies which have allowed today's optimum designs.

Jan 1, 1978

By Nikolas K. Sokol

Underground construction often requires working within a very congested urban environment, including excavating shafts adjacent to highly sensitive and multistoried structures, sometimes even within such structures. Shafts adjacent to heavily loaded column footings are often required due to space constraints. Invariably, footing surcharges must be considered during the design of shaft rock reinforcement. Rockwedge stability evaluation reveals that column surcharges can greatly impact the ability to meet the desired factor of safety. Design methodologies and examples to deal with these special circumstances are presented.

Jan 1, 2008